I have a dell poweredge sc430 (what ever that is). Came cheap with an 80 gig sata hard drive.
So maybe a year later I bought a 250 gig sata drive for backup (with rsynch from cron).
Rsynch works fine.

But now the machine won't reboot without me manually
pressing the F1 key.

I see a message, at boot time, that says something like: "drive one not found, press F1 to continue"
....and if I press F1 and it boots just fine.
I have sata drive0 and drive1 turned on in the bios.
After it does boot, both drives work just fine.
I turned them all on (sata0...5 or something) as an experiment.
But that changed nothing.

Might be a BIOS issue. Have you checked your motherboard BIOS configuration?

Sounds like your BIOS is halting and waiting for keyboard input from an error. If so, you need to instruct your BIOS to continue the boot process upon error (without pressing a key, etc.)

Thanks. I poked around. Turned "keyboard error reporting" to off.
Now it boots just fine (still reports sata drive1 not found, but no longer
busy waits for the F1 key........and it does find sata drive1 just fine,
after reporting the error).

Anyway it boots now. Thank you.

You are welcome